In my opinion (former criminal lawyer) 1) & 2) won't happen, largely becuase it would send an awful message to those who may wish to raise a domestic violence complaint in future. As for 1), I guess there could be a witness summons for her attendance (not even sure the judge/mags would go for that, nor whether the CPS would even ask for one), but if she then appears at court, and takes the stand, the prosecution would have to treat her as a hostile witness and cross examine her on any original statement (is there even one?); as you can imagine, cross-examining your own witness is not a good look, and in the absence of independent evidence, is a tough ask for the prosecutor. Regards 2), there is a potential for it to happen, but would have to be an extreme case (think serious sexual offence allegations).
So we are left with the 999 call, and bodycam (likely only showing any aftermath)...potential for a bad character application perhaps (although hard for me to say without reviewing the file).
Unless I am missing something, this case will be incredibly difficult to secure a conviction on, if it even gets that far and the CPS do offer evidence. The prosecutor on the day will have their work cut out, and will not have been the one who made the decision to charge/progress with the matter. I know there are good policy reasons why domestic abuse convictions should be pursued in the absence of the complainant's support, but that doesn't make it any easier for the lawyer on the day.